This section is intended to introduce various aspects of the art, which may be associated with exemplary embodiments of the present disclosure. This discussion is believed to assist in providing a framework to facilitate a better understanding of particular aspects of the present disclosure. Accordingly, it should be understood that this section should be read in this light, and not necessarily as admissions of prior art.
The root structures of plants are an unseen part of plant physiology. To image and observe plant roots, several methods have been developed. One such method involves removing the plant and its surrounding soil out of the container in which it was growing, washing the soil from the plant roots, and imaging the roots using a desktop flatbed scanner. Another method for imaging plant roots is performed using devices called rhizotrons. These are transparent tubes that are placed in the ground. After plant roots grow around the rhizotron, a visible light camera is placed in the tube for capturing images of the plant roots that are on the external surface of the rhizotron. For example, see M. G. Johnson et al., “Advancing fine root research with minirhizotrons,” Environmental and Experimental Botany, vol. 45, issue 3, pp. 263-289, Apr. 19, 2001; and C. M. Iversen et al., “Advancing the use of minirhizotrons in wetlands,” Plant Soil, vol. 352, issue 1-2, pp. 23-39, Sep. 10, 2011. These methods are glass-wall techniques where the plant roots are visually observed at the wall-soil boundary. Unfortunately, most plant roots are still not visible since a vast majority of the plant roots are not near the glass wall, and the visible cameras cannot see through the soil.
Thus, there is a need to develop technologies to image plant root phenotypes in situ. Currently no technologies exist that have been designed to image plant roots in complex media, such as agricultural field conditions. Even the best existing imaging modalities such as x-ray, MRI, and PET have limitations when imaging different components of complex media, such as soil containing plant roots, minerals, and rocks. Furthermore, none of these technologies are currently deployable in open agricultural fields.
Further information on imaging of plant roots can be found in the following publications, all of which are hereby incorporated by reference herein: N. Seignez et al., “Development of Plant Roots Network in Polluted Soils: An X-ray Computed Microtomography Investigation,” Water Air Soil Pollut., vol. 209, issue 1-4, pp. 199-207, Oct. 16, 2009; and D. Page et al., “Novel X-ray imaging and segmentation of root structures,” Sensor Review, vol. 28, no. 1, pp. 46-51, 2008.
It should be noted that D. Page et al. did not utilize a linear x-ray tube, and their system required a low density, low-attenuation substrate to serve as an artificial medium to support the plant roots, meaning that their system could not use x-ray imaging of plant roots as planted in their native soil.